JP2012182084A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery comprising a filler layer resistant to cracking and peeling to achieve excellent quality stability.SOLUTION: A nonaqueous electrolyte secondary battery in accordance with an embodiment of the present invention comprises a wound electrode body made by winding a positive electrode sheet 10 and a negative electrode sheet with an intervening separator sheet 40. The separator sheet 40 comprises a porous resin sheet 42 and a porous filler layer 44 laminated to at least one side of the resin sheet 42, the filler layer 44 contains a filler composed of an inorganic material, and a binder, the elongation percentage of the resin sheet 42 under a tensile stress of 80 MPa in the longitudinal direction is 160% or lower, and the elongation percentage of the separator sheet 40 including the filler layer 44 under a tensile stress of 80 MPa in the longitudinal direction is in the range of 100% to 115%.

Description

  The present invention relates to a nonaqueous electrolyte secondary battery, and more particularly to a nonaqueous electrolyte secondary battery including a separator sheet provided with a filler layer on a resin sheet.

  In recent years, lithium-ion batteries, nickel-metal hydride batteries, and other secondary batteries have become increasingly important as power sources for vehicles or as power sources for personal computers and portable terminals. In particular, a lithium ion battery that is lightweight and obtains a high energy density is expected to be preferably used as a high-output power source mounted on a vehicle. One typical configuration of this type of lithium secondary battery includes an electrode body (winding electrode body) having a structure in which a sheet-like electrode is wound in a spiral shape. Such a wound electrode body includes, for example, a negative electrode sheet having a structure in which a negative electrode active material layer containing a negative electrode active material is held on both sides of a negative electrode current collector, and a positive electrode active material layer containing a positive electrode active material. And a positive electrode sheet having a structure held on both sides of the sheet is wound in a spiral shape through a separator sheet. As such a separator sheet, a resin sheet made of polyethylene (PE), polypropylene (PP) or the like in which a large number of pores are formed is used in order to ensure ion permeability between the positive and negative electrodes.

  However, a resin sheet made of polyethylene (PE), polypropylene (PP), or the like is likely to be thermally contracted when the temperature inside the battery becomes high, thereby causing a local short circuit, which may further increase the short circuit. Therefore, in order to prevent a short circuit due to thermal contraction of the resin sheet, it has been proposed to laminate a porous heat-resistant filler layer on the surface of the resin sheet. For example, Patent Document 1 describes a technique for forming a coating layer (filler layer) containing filler particles and a binder on the surface of a porous separator body (resin sheet).

JP 2007-280911 A JP 2006-124652 A International Publication No. 2006/061940

  Incidentally, the wound electrode body is generally formed by winding while pulling the positive electrode sheet, the negative electrode sheet, and the separator sheet, and in this case, a processing tension of several tens of MPa is applied in the longitudinal direction of each sheet. Become. However, when a separator sheet having a filler layer formed on the surface of the resin sheet is used as in Patent Document 1, the extensibility (easiness of elongation) of the resin sheet and the filler layer is significantly different. In some cases, the filler layer cannot follow the elongation of the resin sheet due to the tension, and the filler layer is cracked and cracked, or the filler layer is peeled off from the resin sheet.

  Accordingly, the present invention provides a nonaqueous electrolyte secondary battery that is excellent in quality stability and is less likely to cause cracking or peeling in the filler layer in a nonaqueous electrolyte secondary battery including the separator sheet as described above. One purpose. Another object is to provide a method for producing such a non-aqueous electrolyte secondary battery.

  The nonaqueous electrolyte secondary battery according to the present invention is a nonaqueous electrolyte secondary battery including a wound electrode body in which a positive electrode sheet and a negative electrode sheet are wound through a separator sheet. The separator sheet includes a porous resin sheet and a porous filler layer laminated on at least one surface of the resin sheet. The filler layer includes a filler made of an inorganic material and a binder. The elongation when a tensile stress of 80 MPa is applied in the longitudinal direction of the resin sheet is 160% or less, preferably 150% or less. Furthermore, the elongation when a tensile stress of 80 MPa is applied in the longitudinal direction of the separator sheet including the filler layer is 100% to 115%, preferably 100% to 110%.

  According to the configuration of the present invention, an elongation rate when a tensile stress of 80 MPa is applied in the longitudinal direction of the resin sheet (hereinafter, also simply referred to as “elongation rate”) is 160% or less, and the separator includes a filler layer. By setting the elongation rate (hereinafter also simply referred to as “elongation rate”) when a tensile stress of 80 MPa is applied in the longitudinal direction of the sheet to 100% to 115%, the extensibility (easiness of elongation) of the filler layer is achieved. Since it approaches the resin sheet, the filler layer can sufficiently follow the elongation of the resin sheet due to the processing tension. Therefore, a non-aqueous electrolyte secondary battery that is not easily cracked or peeled off in the wound electrode body forming step and has excellent quality stability can be obtained.

In one preferable aspect of the nonaqueous electrolyte secondary battery disclosed herein, the weight (weight per unit area) of the filler layer per unit area of the resin sheet is 0.4 mg / cm ^{2 to} 0.9 mg / cm ^2. It is. If the weight of the filler layer (weight) is too small, it will be difficult to adjust the elongation of the separator sheet within a suitable range, and the effect of suppressing thermal shrinkage of the resin sheet will be reduced, and short circuit prevention will be prevented. The effect may be reduced. On the other hand, if the filler layer is too heavy (weight), in addition to the filler layer being easily broken, the electrical resistance of the separator sheet is increased, and battery characteristics (such as charge / discharge characteristics) may be deteriorated.

  In one preferable aspect of the nonaqueous electrolyte secondary battery disclosed herein, the porosity of the resin sheet is 30% to 50%. If the porosity of the resin sheet is too large, it becomes difficult to adjust the elongation percentage of the resin sheet to a suitable range, and the strength is insufficient, and there is a possibility that film breakage is likely to occur. On the other hand, if the porosity of the resin sheet is too small, the amount of the electrolyte solution that can be held in the separator sheet decreases, and the ionic conductivity may decrease.

  In a preferable aspect of the nonaqueous electrolyte secondary battery disclosed herein, the resin sheet is made of a polyolefin resin. In another preferred embodiment, the resin sheet is a porous resin sheet that is uniaxially or biaxially stretched. Such a porous resin sheet is particularly preferable because it makes it easy to adjust the elongation percentage of the resin sheet to a suitable range, and also has an appropriate strength and little thermal shrinkage in the width direction.

  In a preferable aspect of the nonaqueous electrolyte secondary battery disclosed herein, the filler is made of at least one material selected from the group consisting of alumina, boehmite, magnesia, and titania. According to these inorganic compounds, in addition to the ease of adjusting the elongation of the separator sheet including the filler layer to a suitable range, it is possible to suitably ensure the heat resistance and mechanical strength of the separator sheet. it can.

  In a preferred aspect of the nonaqueous electrolyte secondary battery disclosed herein, the binder is made of a polymer that is dispersed or dissolved in an aqueous solvent. A polymer that is dispersed or dissolved in an aqueous solvent is preferable in that it does not react or cure with moisture in the air, and thus the extensibility of the filler layer can be easily adjusted (for example, without performing moisture management during production).

  As another aspect of the present invention, a method for producing a nonaqueous electrolyte secondary battery is provided. This manufacturing method includes a step of forming a separator sheet by laminating a filler layer containing a filler made of an inorganic material and a binder on one surface of a resin sheet. Moreover, the process of winding up the separator sheet containing the said filler layer in roll shape, and forming a separator roll is included. Further, the method includes a step of constructing a wound electrode body using the separator sheet drawn out from the separator roll. And when winding up the said separator sheet containing the said filler layer in roll shape and forming the said separator roll, winding up so that the surface by the side of the filler layer of this separator sheet may face the inner peripheral side of the said separator roll Features.

  If the surface is wound so that the surface on the filler layer side faces the outer peripheral side, stress acts in the direction in which the filler layer is extended during winding, so that defects such as cracks and peeling may occur in the filler layer. Even if such a defect does not occur immediately after winding, it tends to occur when the separator roll is stored for a long period of time. On the other hand, in the said structure, it winds up so that the surface by the side of a filler layer may face the inner peripheral side of a separator roll. By taking up the filler layer so that the surface on the filler layer side faces the inner periphery, stress acts in the direction of shrinking the filler layer, and no stress is applied in the direction of extension. Therefore, it is possible to suppress the occurrence of defects such as cracks and peeling in the filler layer.

  As described above, any of the nonaqueous electrolyte secondary batteries disclosed herein is suitably suppressed from performance degradation due to the peeling of the filler layer, etc., so that the nonaqueous electrolyte secondary battery mounted on the vehicle is With performance suitable as a battery. Therefore, according to this invention, a vehicle provided with the nonaqueous electrolyte secondary battery disclosed here is provided. In particular, a vehicle (for example, an automobile) including the nonaqueous electrolyte secondary battery as a power source (typically, a power source of a hybrid vehicle or an electric vehicle) is provided.

1 is a perspective view schematically showing a nonaqueous electrolyte secondary battery according to an embodiment of the present invention. It is sectional drawing which shows the II-II cross section of FIG. 1 typically. It is a schematic diagram for demonstrating the wound electrode body which concerns on one Embodiment of this invention. It is a front view which shows typically the wound electrode body which concerns on one Embodiment of this invention. It is sectional drawing which shows typically the principal part of the wound electrode body which concerns on one Embodiment of this invention. 1 is a side view schematically showing a vehicle equipped with a nonaqueous electrolyte secondary battery according to an embodiment of the present invention.

  Embodiments according to the present invention will be described below with reference to the drawings. In the following drawings, members / parts having the same action are described with the same reference numerals. Note that the dimensional relationship (length, width, thickness, etc.) in each drawing does not reflect the actual dimensional relationship. Further, matters other than the matters specifically mentioned in the present specification and matters necessary for carrying out the present invention (for example, the configuration and manufacturing method of an electrode body including a positive electrode and a negative electrode, the configuration and manufacturing method of a separator and an electrolyte, Non-aqueous electrolyte secondary battery and other general techniques related to the construction of batteries, etc.) can be grasped as design matters of those skilled in the art based on the prior art in this field.

  Although not intended to be particularly limited, in the following, a nonaqueous electrolyte lithium secondary battery (lithium) in a form in which a wound electrode body (rolled electrode body) and a nonaqueous electrolyte are housed in a rectangular container The present invention will be described in detail by taking an ion secondary battery as an example.

<Lithium secondary battery>
A schematic configuration of a lithium secondary battery according to an embodiment of the present invention is shown in FIGS. The lithium secondary battery 100 includes an electrode body (rolled electrode body) 80 in which a long positive electrode sheet 10 and a long negative electrode sheet 20 are wound through a long separator sheet 40. In addition to the non-aqueous electrolyte (non-aqueous electrolyte) (not shown), the wound electrode body 80 is housed in a container 50 having a shape (square shape) that can accommodate the wound electrode body 80.

  The container 50 includes a bottomed rectangular container main body 52 having an open upper end, and a lid 54 that closes the opening. As a material constituting the container 50, a metal material such as aluminum, steel, or Ni-plated SUS is preferably used (Ni-plated SUS in the present embodiment). Or the container 50 formed by shape | molding resin materials, such as PPS and a polyimide resin, may be sufficient. On the upper surface of the container 50 (that is, the lid body 54), a positive electrode terminal 70 that is electrically connected to the positive electrode 10 of the wound electrode body 80 and a negative electrode terminal 72 that is electrically connected to the negative electrode 20 of the wound electrode body 80 are provided. It has been.

  The wound electrode body 80 according to the present embodiment is the same as the wound electrode body of a normal lithium secondary battery except for the configuration of the separator sheet 40 described later, and as shown in FIG. In the stage before assembling 80, it has a long (strip-shaped) sheet structure.

  The positive electrode sheet 10 has a structure in which a positive electrode active material layer 14 containing a positive electrode active material is held on both surfaces of a long sheet-like foil-shaped positive electrode current collector 12. However, the positive electrode active material layer 14 is not attached to one side edge (the upper side edge portion in the figure) along the edge in the width direction of the positive electrode sheet 10, and the positive electrode current collector 12 is exposed with a certain width. A positive electrode active material layer non-formed part is formed.

  Similarly to the positive electrode sheet 10, the negative electrode sheet 20 has a structure in which a negative electrode active material layer 24 containing a negative electrode active material is held on both surfaces of a long sheet-like foil-shaped negative electrode current collector 22. However, the negative electrode active material layer 24 is not attached to one side edge (the lower side edge portion in the drawing) along the edge in the width direction of the negative electrode sheet 20, and the negative electrode current collector 22 has a constant width. An exposed negative electrode active material layer non-forming portion is formed.

  When producing the wound electrode body 80, the positive electrode sheet 10 and the negative electrode sheet 20 are laminated via the separator sheet 40 as shown in FIG. 3. At this time, the positive electrode sheet 10 and the negative electrode sheet 20 are formed such that the positive electrode active material layer non-formed portion of the positive electrode sheet 10 and the negative electrode active material layer non-formed portion of the negative electrode sheet 20 protrude from both sides in the width direction of the separator sheet 40. Are overlapped slightly in the width direction. In this way, the positive electrode sheet 10 and the negative electrode sheet 20 are overlapped through the separator sheet 40, and the wound electrode body 80 is produced by winding each of the sheets 10, 20, and 40 in the longitudinal direction of the sheet while pulling. Can be done.

  A wound core portion 82 (that is, the positive electrode active material layer 14 of the positive electrode sheet 10, the negative electrode active material layer 24 of the negative electrode sheet 20, and the separator sheet 40) is densely arranged in the central portion of the wound electrode body 80 in the winding axis direction. Laminated portions) are formed. In addition, the electrode active material layer non-formed portions of the positive electrode sheet 10 and the negative electrode sheet 20 protrude outward from the wound core portion 82 at both ends in the winding axis direction of the wound electrode body 80. A positive electrode lead terminal 74 and a negative electrode lead terminal 76 (see FIG. 5) are provided on the positive electrode side protruding portion (that is, the non-formed portion of the positive electrode active material layer 14) 84 and the negative electrode side protruding portion (that is, the non-formed portion of the negative electrode active material layer 24) 4), and are electrically connected to the positive terminal 70 and the negative terminal 72, respectively.

  The constituent elements of the wound electrode body 80 may be the same as those of a conventional wound electrode body of a lithium secondary battery except for a separator sheet 40 described later, and are not particularly limited. For example, the positive electrode sheet 10 may be formed by applying a positive electrode active material layer 14 mainly composed of a positive electrode active material for a lithium secondary battery on a long positive electrode current collector 12.

  For the positive electrode current collector 12, an aluminum foil or other metal foil suitable for the positive electrode is preferably used. In the present embodiment, a sheet-like aluminum positive electrode current collector 12 is used. For example, an aluminum sheet having a thickness of about 10 μm to 30 μm can be suitably used.

The positive electrode active material layer 14 is composed of a positive electrode active material and other positive electrode active material layer forming components (for example, a binder, a conductive material, etc.) used as necessary. As the positive electrode active material, one type or two or more types of materials conventionally used in lithium secondary batteries can be used without any particular limitation. As a preferable application object of the technology disclosed herein, lithium and a transition metal element such as lithium nickel oxide (LiNiO ₂ ), lithium cobalt oxide (LiCoO ₂ ), and lithium manganese oxide (LiMn ₂ O ₄ ) are used. A positive electrode active material mainly containing an oxide containing a constituent metal element (lithium transition metal oxide) can be given. Among them, a positive electrode active material (typically, substantially a lithium nickel cobalt manganese composite oxide substantially composed of lithium nickel cobalt manganese composite oxide (for example, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ). Application to a positive electrode active material comprising: An olivine type lithium phosphate represented by the general formula LiMPO ₄ (M is at least one element of Co, Ni, Mn, Fe; for example, LiFeO ₄ , LiMnPO ₄ ) may be used as the positive electrode active material. .

  As such a lithium transition metal compound (typically in particulate form), for example, a lithium transition metal compound powder prepared by a conventionally known method can be used as it is. For example, a lithium transition metal compound powder substantially composed of secondary particles having an average particle diameter in the range of about 1 μm to 25 μm can be preferably used as the positive electrode active material. The amount of the positive electrode active material contained in the positive electrode active material layer can be appropriately selected, and can be, for example, 80% by mass to 95% by mass.

  Similarly to the positive electrode sheet 10, the negative electrode sheet 20 is formed by attaching a negative electrode active material layer 24 to both surfaces of a long sheet-like foil-shaped negative electrode current collector 22. However, the negative electrode active material layer 24 is not attached to one side edge along the edge in the width direction of the sheet-like electrode body, and the negative electrode current collector 22 is exposed with a certain width.

  For the negative electrode current collector 22, a metal foil suitable for copper foil (this embodiment) and other negative electrodes is preferably used. In the present embodiment, a sheet-like copper negative electrode current collector 22 is used. For example, a copper sheet having a thickness of about 5 μm to 30 μm can be suitably used.

  The negative electrode active material layer 24 is composed of a negative electrode active material and other negative electrode active material layer forming components (such as a binder) used as necessary. As the negative electrode active material, one type or two or more types of materials conventionally used in lithium secondary batteries can be used without any particular limitation. Preferable examples include carbon-based materials such as graphite carbon and amorphous carbon (graphite in the present embodiment), lithium-containing transition metal oxides, transition metal nitrides, and the like. The amount of the negative electrode active material contained in the negative electrode active material layer is not particularly limited, but is preferably about 90% by mass to 99% by mass, more preferably about 95% by mass to 99% by mass.

<Separator sheet>
Next, the separator sheet 40 will be described. FIG. 5 is a schematic cross-sectional view showing an enlarged part of a cross section along the winding axis of the wound electrode body 80 according to the embodiment, and is a separator sheet 40 and a positive electrode sheet facing the separator sheet 40. 10 is shown. As shown in FIG. 5, the separator sheet 40 is formed in a long sheet shape. The separator sheet 40 includes a porous resin sheet 42 and a porous filler layer 44 laminated on at least one surface (here, one surface) of the resin sheet 42. The filler layer 44 includes a filler (for example, alumina) made of an inorganic material and a binder. The elongation when a tensile stress of 80 MPa is applied in the longitudinal direction (MD direction) of the resin sheet 42 is 160% or less, preferably 150% or less. Further, the elongation when a tensile stress of 80 MPa is applied in the longitudinal direction (MD direction) of the separator sheet 40 including the filler layer 44 is 100% to 115%, preferably 100% to 110%. Here, the longitudinal direction of the resin sheet 42 is the same as the winding direction of the wound electrode body 80. The filler layer 44 can be provided on both sides of the separator sheet 40.

  As described above, the separator sheet including the filler layer 44 having an elongation rate (hereinafter, also simply referred to as “elongation rate”) of 160% or less when a tensile stress of 80 MPa is applied in the longitudinal direction of the resin sheet 42. The extensibility (easiness of elongation) of the filler layer 44 is set to 100% to 115% when the tensile stress of 80 MPa is applied in the longitudinal direction of 40 (hereinafter also referred to as “elongation rate”). Therefore, the filler layer 44 can sufficiently follow the elongation of the resin sheet 42 due to the processing tension. Therefore, the non-aqueous electrolyte secondary battery 100 excellent in quality stability can be obtained because the filler layer 44 is hardly cracked or peeled off even in the wound electrode body forming step.

  For example, the longitudinal elongation of the resin sheet 42 is preferably 160% or less (for example, 100% to 160%), more preferably 150% or less (for example, 100% to 150%). Further, those satisfying 140% or less (for example, 100% to 140%) are more preferable, and those satisfying 130% or less (for example, 100% to 130%) are particularly preferable. When the elongation percentage of the resin sheet 42 is too larger than 160%, the extensibility of the resin sheet 42 and the filler layer 44 is remarkably different, so that defects due to cracking or peeling of the filler layer 44 occur in the wound electrode body forming process. It is possible that The elongation percentage of the resin sheet 42 can be calculated as follows. A rectangular test piece of 10 cm in the longitudinal direction and 1 cm in the width direction is taken from the resin sheet 42, and a mark with a predetermined interval (L 0) is marked at the center in the longitudinal direction. Both ends of the test piece are fixed to a chuck of a tensile tester, a load is applied so that a tensile stress of 80 MPa is applied to the lower end, and the gauge interval (L) is measured. At this time, the elongation percentage of the resin sheet 42 can be calculated by L / L0 × 100.

  The resin sheet 42 satisfying the elongation rate value can be realized, for example, by adjusting the porosity of the resin sheet 42. Increasing the porosity of the resin sheet 42 increases the elongation, and decreasing the porosity of the resin sheet 42 tends to decrease the elongation. Therefore, by appropriately adjusting the porosity of the resin sheet 42, it is possible to form a resin sheet satisfying an elongation value of 160% or less. In addition, as a method for controlling the elongation rate of the resin sheet 42, a method such as changing the heat treatment method or changing the density of the material (PE, PP, etc.) constituting the resin sheet can be adopted.

  Further, the elongation in the longitudinal direction of the separator sheet 40 including the filler layer 44 is preferably 115% or less, more preferably 111% or less, and more preferably 110% or less. And those satisfying 108% or less are particularly preferred. When the elongation percentage of the separator sheet 40 is too larger than 115%, the extensibility of the filler layer 44 and the resin sheet 42 is remarkably different, so that a defect due to cracking or peeling of the filler layer 44 occurs in the wound electrode body forming process. It is possible that On the other hand, the separator sheet 40 having an elongation value of less than 100% is substantially impossible to manufacture. For example, a separator sheet 40 having an elongation value of 100 to 115% is appropriate from the viewpoint of preventing the filler layer 44 from slipping. The elongation percentage of the separator sheet 40 including the filler layer 44 can be calculated in the same manner as the elongation percentage of the resin sheet 42. That is, a rectangular test piece of 10 cm in the longitudinal direction and 1 cm in the width direction is taken from the separator sheet 40 including the filler layer 44, and a mark with a predetermined interval (L 0) is written at the center in the longitudinal direction. Both ends of the test piece are fixed to a chuck of a tensile tester, a load is applied so that a tensile stress of 80 MPa is applied to the lower end, and the gauge interval (L) is measured. At this time, the elongation percentage of the separator sheet 40 can be calculated by L / L0 × 100.

  The separator sheet 40 including the filler layer 44 that satisfies the elongation rate value can be realized, for example, by adjusting the weight (weight per unit area) of the filler layer 44 per unit area of the resin sheet 42. When the basis weight of the filler layer 44 is formed larger, the elongation rate of the separator sheet 40 including the filler layer 44 becomes smaller, and when the basis weight of the filler layer 44 is formed smaller, the elongation rate of the separator sheet 40 including the filler layer 44 increases. Tend to be. Therefore, by appropriately adjusting the basis weight of the filler layer 44, it is possible to form the separator sheet 40 including the filler layer 44 that satisfies an elongation value of 100 to 115%. In addition, as a method for controlling the elongation percentage of the separator sheet 40 including the filler layer 44, a method such as changing the type of the binder constituting the filler layer or changing the density of the filler layer can be employed.

  As a material of the resin sheet 42, for example, a polyolefin resin such as polyethylene (PE) or polypropylene (PP) can be suitably used. The structure of the resin sheet 42 may be a single layer structure or a multilayer structure. FIG. 5 shows an example of a resin sheet 42 having a single layer structure. Here, the resin sheet 42 is made of a polyethylene (PE) resin. As the polyethylene (PE) resin, a homopolymer of ethylene is preferably used. According to such a configuration, it becomes easy to adjust the elongation percentage of the resin sheet 42 to a suitable range. Polyethylene (PE) resin is a resin containing 50% by mass or more of repeating units derived from ethylene, and is a copolymer obtained by polymerizing an α-olefin copolymerizable with ethylene, or copolymerized with ethylene. A copolymer obtained by polymerizing at least one possible monomer may be used. Examples of the α-olefin include propylene. Examples of other monomers include conjugated dienes (for example, butadiene) and acrylic acid.

  Moreover, it is preferable that the resin sheet 42 is comprised from PE whose shutdown temperature is about 120 to 140 degreeC (typically 125 to 135 degreeC). The shutdown temperature is sufficiently lower than the temperature at which the battery 100 is thermally runaway (for example, about 1000 ° C. or higher). Examples of such PE include polyesters generally referred to as high-density polyethylene or linear (linear) low-density polyethylene. Alternatively, various types of branched polyethylene having medium density and low density may be used. Moreover, additives, such as various plasticizers and antioxidants, can also be contained as needed.

  As the resin sheet 42, a uniaxially stretched or biaxially stretched porous resin sheet can be suitably used. Among them, the porous resin sheet uniaxially stretched in the longitudinal direction (MD direction: Machine Direction) has an appropriate strength in addition to making it easy to adjust the elongation of the resin sheet 42 to a suitable range. It is particularly preferable because it has little thermal shrinkage in the width direction while being provided. For example, when a separator sheet having such a uniaxially stretched resin sheet in the longitudinal direction is used, thermal contraction in the longitudinal direction can be suppressed in a mode in which the sheet is wound together with a long sheet-like positive electrode and negative electrode. Therefore, the porous resin sheet uniaxially stretched in the longitudinal direction is particularly suitable as a material for the separator sheet constituting the wound electrode body.

  The thickness of the resin sheet 42 is preferably about 10 μm to 30 μm, and more preferably about 15 μm to 25 μm. If the thickness of the resin sheet 42 is too large, the ion conductivity of the separator sheet 40 may be reduced. On the other hand, if the thickness of the resin sheet 42 is too small, it becomes difficult to adjust the elongation of the resin sheet 42 to a suitable range, and there is a possibility that a film breakage may occur. In addition, the thickness of the resin sheet 42 can be calculated | required by image-analyzing the image image | photographed with the scanning electron microscope (SEM).

The porosity of the resin sheet 42 is preferably about 20% to 60%, and more preferably about 30% to 50%, for example. If the porosity of the resin sheet 42 is too large, it becomes difficult to adjust the elongation rate of the resin sheet 42 to a suitable range, and the strength is insufficient, and there is a possibility that film breakage is likely to occur. On the other hand, if the porosity of the resin sheet 42 is too small, the amount of the electrolyte solution that can be held in the separator sheet 40 decreases, and the ionic conductivity may decrease. The porosity of the resin sheet 42 can be calculated as follows. The apparent volume occupied by the resin sheet 42 of unit area (size) is V1 [cm ³ ], and the mass of the resin sheet 42 of the unit area is W [g]. The ratio of the mass W to the true density ρ [g / cm ³ ] of the resin material constituting the resin sheet 42, that is, W / ρ is V0. V0 is the volume occupied by the dense body of the resin material with mass W. At this time, the porosity of the resin sheet 42 can be calculated by [(V1-V0) / V1] × 100.

  In addition, although the resin sheet 42 is comprised by the single layer structure of PE layer here, the resin sheet of a multilayer structure may be sufficient. For example, you may comprise by 3 layer structure of PP layer, PE layer laminated | stacked on PP layer, and PP layer laminated | stacked on PE layer. In this case, the filler layer can be laminated on the PP layer. The number of layers of the resin sheet having a multilayer structure is not limited to 3, and may be 2 or 4 or more.

  The filler layer 44 laminated on one surface of the resin sheet 42 includes a filler made of an inorganic material and a binder. Next, the filler layer 44 will be described. In this embodiment, the filler layer 44 is formed in a region facing the positive electrode active material layer 14 of the positive electrode sheet 10.

As the filler (filler) used for the filler layer 44, an inorganic material having high electrical insulation and a melting point higher than that of the resin sheet 42 (for example, 190 ° C. or higher) can be suitably used. The material can be, for example, a metal oxide, hydroxide, nitride, or the like. The form of the inorganic material can be in the form of particles, fibers, flakes, and the like. Usually, it is preferable to use a particulate inorganic material. Particles made of inorganic oxide or inorganic hydroxide can be suitably used. For example, one or two or more inorganic oxides selected from alumina, boehmite, magnesia, titania, silica, zirconia, zinc oxide, iron oxide, ceria, yttria and the like can be used. Particularly preferred inorganic compounds include alumina, boehmite, magnesia and titania. According to these inorganic compounds, it becomes easy to adjust the elongation of the separator sheet 40 including the filler layer 44 within a suitable range, and in addition, the heat resistance and mechanical strength of the separator sheet 40 are suitably ensured. be able to. The primary particle diameter of the inorganic compound particles can be, for example, about 0.15 μm to ² μm, and the specific surface area can be about ² to 13 m ² / g.

  The binder used for the filler layer 44 is an aqueous solvent when the filler layer-forming paint described later is an aqueous solvent (a solution using water or a mixed solvent containing water as a main component as a binder dispersion medium). A polymer that can be dispersed or dissolved in can be used. Examples of the polymer that is dispersed or dissolved in the aqueous solvent include acrylic resins. As acrylic resin, monomers such as acrylic acid, methacrylic acid, acrylamide, methacrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, methacrylate, methyl methacrylate, ethylhexyl acrylate, butyl acrylate, etc. were polymerized in one kind. A homopolymer is preferably used. The acrylic resin may be a copolymer obtained by polymerizing two or more of the above monomers. Further, a mixture of two or more of the above homopolymers and copolymers may be used. In addition to the acrylic resin described above, polyolefin resins such as styrene butadiene rubber (SBR) and polyethylene (PE), carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), and the like can be used. These polymers can be used alone or in combination of two or more. Among them, it is preferable to use acrylic resin, styrene butadiene rubber, and polyolefin resin. These water-based binders are preferable in that they do not react and harden with moisture in the atmosphere and can easily adjust the extensibility of the filler layer (for example, without performing water management during production). The average particle size of the binder is, for example, about 0.09 μm to 0.15 μm. The form of the binder is not particularly limited, and a particulate (powdered) one may be used as it is, or one prepared in a solution or emulsion may be used. Two or more kinds of binders may be used in different forms.

  In addition, the binder used for the filler layer 44 is dispersed or dissolved in a solvent-based solvent when the filler layer-forming paint described later is a solvent-based solvent (a solution in which the binder dispersion medium is mainly an organic solvent). Can be used. Examples of the polymer that is dispersed or dissolved in the solvent-based solvent include a polyvinylidene fluoride-based resin composition. As the polyvinylidene fluoride resin, a homopolymer of vinylidene fluoride is preferably used. Furthermore, as the polyvinylidene fluoride resin, a copolymer of a vinyl monomer copolymerizable with vinylidene fluoride is also preferably used. Examples of vinyl monomers copolymerizable with vinylidene fluoride include hexafluoropropylene, tetrafluoroethylene, and ethylene trichloride fluoride. Alternatively, polytetrafluoroethylene (PTFE), polyacrylonitrile, polymethyl methacrylate, or the like is preferably used as a polymer that is dispersed or dissolved in a solvent-based solvent. These solvent-based binders are preferable in that the extensibility of the filler layer 44 can be suitably improved. However, since the solvent-based binder reacts with moisture in the atmosphere and cures, it is necessary to perform moisture management during production.

  Although not particularly limited, the proportion of the filler in the entire filler layer 44 is preferably about 90% by mass or more (typically 95% by mass to 99% by mass), preferably about 97% by mass to 99% by mass. It is preferable that The proportion of the binder in the filler layer 44 is preferably about 7% by mass or less, and preferably about 5% by mass or less (eg, about 0.5% to 3% by mass). Moreover, when it contains filler layer forming components (for example, thickener etc.) other than a filler and a binder, it is preferable that the total content rate of these arbitrary components shall be about 3 mass% or less, and about 2 mass% or less (for example, It is preferable to set it to about 0.5 mass% to 1 mass%. If the proportion of the binder is too small, it becomes difficult to adjust the elongation of the separator sheet 40 including the filler layer 44 within a suitable range. In addition, the anchoring property of the filler layer 44 and the filler layer 44 are increased. The strength (shape retention) of itself may decrease, and defects such as cracks and peeling off may occur. When the ratio of the binder is too large, the porosity of the filler layer 44 is insufficient, and the ion permeability of the separator sheet 40 including the filler layer 44 is lowered (and thus a secondary structure constructed using the separator sheet 40). Battery resistance may increase).

  The thickness of the filler layer 44 is preferably about 1 μm to 12 μm, and more preferably about 2 μm to 8 μm. When the thickness of the filler layer 44 is too small, it becomes difficult to adjust the elongation of the separator sheet 40 including the filler layer 44 to a suitable range, and the electrolytic solution that can reduce or retain the short circuit prevention effect The amount may decrease. On the other hand, when the thickness of the filler layer 44 is too large, cracking of the filler layer is likely to occur, and in addition, the electrical resistance of the separator sheet increases, and battery characteristics (such as charge / discharge characteristics) may be deteriorated. The thickness of the filler layer 44 can be obtained by image analysis of an image taken with a scanning electron microscope (SEM).

The weight of the filler layer 44 per unit area of the resin sheet 42 (basis weight) ^is preferably 0.4g / cm ² ~0.9g / cm 2 approximately, 0.5g ^/ cm 2 ~0.8g ^/ More preferably, it is about cm ² . If the weight (weight per unit area) of the filler layer 44 is too small, it becomes difficult to adjust the elongation rate of the separator sheet 40 including the filler layer 44 to a suitable range, and the thermal contraction of the resin sheet 42 is suppressed. The effect may be reduced, and the short-circuit prevention effect may be reduced. On the other hand, when the weight (weight) of the filler layer 44 is too large, the electrical resistance of the separator sheet 40 increases and battery characteristics (such as charge / discharge characteristics) may be deteriorated.

  Next, a method for forming the filler layer 44 according to this embodiment will be described. As the filler layer-forming coating material for forming the filler layer 44, a paste-like (including slurry-like or ink-like, the same applies hereinafter) in which filler, binder and solvent are mixed and dispersed is used. The filler layer 44 can be formed by applying an appropriate amount of this paste-like paint on the surface of the resin sheet 42 and further drying it.

  Examples of the solvent used in the filler layer-forming coating material include water or a mixed solvent mainly composed of water. As a solvent other than water constituting such a mixed solvent, one or more organic solvents (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water can be appropriately selected and used. Alternatively, organic solvents such as N-methylpyrrolidone (NMP), pyrrolidone, methyl ethyl ketone, methyl isobutyl ketone, ixahexanone, toluene, dimethylformamide, dimethylacetamide, or a combination of two or more of these may be used. The content of the solvent in the filler layer-forming coating material is not particularly limited, but is preferably 40 to 90% by mass, particularly about 50% by mass of the entire coating material.

  The said coating material for filler layer formation can contain the 1 type, or 2 or more types of material which can be used as needed other than a filler and a binder. An example of such a material is a polymer that functions as a thickener for the coating material for forming an inorganic filler layer. In particular, when an aqueous solvent is used, it is preferable to contain a polymer that functions as the thickener. As the polymer functioning as the thickener, carboxymethyl cellulose (CMC) or polyethylene oxide (PEO) is preferably used.

  The operation of mixing the filler and binder with the solvent can be performed using an appropriate kneader such as a disper mill, a clear mix, a fill mix, a ball mill, a homodisper, or an ultrasonic disperser. The filler layer 44 can be formed by applying the coating material for forming the filler layer to the surface of the resin sheet 42 and drying it.

  The operation of applying the filler layer-forming paint on the surface of the resin sheet 42 can be used without any particular limitation on conventional general application means. For example, using a suitable coating device (gravure coater, slit coater, die coater, comma coater, dip coat, etc.), a predetermined amount of the filler layer forming paint is uniformly formed on one surface of the resin sheet. It can be applied by coating. Thereafter, the coating material is dried by a suitable drying means (typically a temperature lower than the melting point of the resin sheet, for example, 110 ° C. or less, for example, 30 to 80 ° C.), thereby removing the solvent in the filler layer forming coating material. To do. By removing the solvent from the filler layer-forming coating material, the filler layer 44 containing a filler and a binder can be formed. In this way, it is possible to obtain the separator sheet 40 in which the filler layer 44 including the filler made of an inorganic material and the binder is formed on one surface of the resin sheet 42.

  Thus, after forming the separator sheet 40 containing the filler layer 44, this separator sheet 40 is wound up in roll shape around the axis | shaft of a core. Thereby, a separator roll is produced. This separator roll is obtained by winding the separator sheet 40 into a roll shape, and can be used in a post-process (rolled electrode body forming process) or stored for a long time in that state. In this embodiment, after the filler layer 44 is continuously formed on the surface of the resin sheet 42, the filler layer 44 is continuously wound around the core on the same production line. Moreover, in that case, it winds up so that the surface by the side of the filler layer 44 of the separator sheet 40 may face the inner peripheral side of a separator roll.

  Here, if winding is performed so that the surface on the filler layer 44 side faces the outer peripheral side of the separator roll, stress acts in a direction in which the filler layer 44 extends during winding, so that the filler layer 44 has defects such as cracks and peeling. Can happen. Even if such a defect does not occur immediately after winding, it tends to occur when the separator roll is stored for a long period of time. On the other hand, in this embodiment, it winds up so that the surface by the side of the filler layer 44 may face the inner peripheral side of a separator roll. By taking up the filler layer 44 so that the surface on the filler layer 44 side is directed toward the inner peripheral side, stress acts in the direction in which the filler layer 44 contracts, and no stress is applied in the direction in which the filler layer 44 extends. Therefore, it is possible to suppress the occurrence of defects such as cracks and peeling in the filler layer 44.

The separator roll thus obtained is subjected to the next wound electrode body forming step. In the wound electrode body forming step, two separator sheets 40 (separator sheet 40 including a filler layer 44) continuously drawn from the separator roll, and separately prepared positive electrode sheet 10 and negative electrode sheet 20 are shown in FIG. As shown in FIG. 5, a wound type wound electrode body 80 for a lithium secondary battery is constructed by overlapping. Thus, as shown in FIGS. 1 and 2, the wound electrode body 80 is accommodated in the main body 52 from the upper end opening of the container main body 52, and an electrolytic solution containing an appropriate electrolyte is disposed in the container main body 52. (Inject). The electrolyte is lithium salt such as LiPF _6, for example. For example, a non-aqueous electrolyte (non-aqueous electrolysis) such as an appropriate amount (for example, concentration 1M) of a lithium salt such as LiPF ₆ is used as a mixed solvent of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (for example, a mass ratio of 3: 4: 3). And can be used as an electrolytic solution.

  Thereafter, the opening is sealed by welding or the like with the lid 54, and the assembly of the lithium secondary battery 100 according to the present embodiment is completed. The process of sealing the container 50 and the process of placing (injecting) the electrolyte may be the same as those used in the production of a conventional lithium secondary battery, and do not characterize the present invention. In this way, the construction of the lithium secondary battery 100 according to this embodiment is completed.

  The lithium secondary battery 100 constructed in this manner exhibits excellent battery performance because the performance deterioration due to the peeling or cracking of the filler layer 44 is suitably suppressed as described above. For example, a battery that satisfies at least one (preferably all) of excellent quality stability, high safety, and low IV resistance can be provided.

  Examples of the present invention will be described below, but the present invention is not intended to be limited to those shown in the following test examples.

<Example 1>
A resin sheet made of polyethylene having a thickness of 20 μm, a porosity of 33%, and an 80 MPa elongation of 114% was used as the resin sheet of Example 1. Alumina powder (Sumitomo Chemical Co., Ltd., “AKP3000”), an acrylic binder, and CMC (Daiichi Kogyo Seiyaku Co., Ltd., “BSH6”) as a thickener have a solid mass ratio of 98. : 1.3: 0.7 and added to water so that the solid content (NV) is 50% by mass, and kneaded with a kneader (“Disper Mill” manufactured by ROBO MICS) to form a filler layer A paint was prepared. The kneading time was 15 minutes at 5000 rpm.

The said coating material was apply | coated to the single side | surface of the said resin sheet using the gravure coating method, and it was made to dry and the filler layer was formed. In the gravure coating, the line speed of the resin sheet was 3 m / min, the gravure roll speed was 3.8 m / min, and the speed ratio (gravure speed / line speed) was 1.27. The drying temperature was 70 ° C. The basis weight of the filler layer after drying (weight of the filler layer per unit area of the resin sheet) was 0.82 mg / cm ² . The thickness of the filler layer was 4 μm. The obtained separator sheet was wound up into a roll shape to produce a separator roll. In that case, it wound up so that the surface by the side of a filler layer might face the inner peripheral side of a separator roll. The winding length of the separator sheet was 200 m.

<Example 2>
A separator roll was produced in the same manner as in Example 1 except that the basis weight of the filler layer was 0.96 mg / cm ² and the thickness was 5 μm.

<Example 3>
Except that a resin sheet made of polyethylene having a basis weight of the filler layer of 0.49 mg / cm ² , a thickness of 2.5 μm, a porosity of 38%, and an 80 MPa elongation rate of 128% was used, the same as in Example 1. A separator roll was prepared.

<Example 4>
A separator roll was produced in the same manner as in Example 3 except that the filler layer side was wound so that the outer surface of the separator roll faced.

<Example 5>
Except that a resin sheet made of polyethylene having a basis weight of the filler layer of 0.51 mg / cm ² , a thickness of 2.5 μm, a porosity of 44%, and an 80 MPa elongation of 141% was used, the same as in Example 1. A separator roll was prepared.

<Example 6>
A separator roll was produced in the same manner as in Example 5 except that the filler layer was wound so that the surface on the filler layer side faced the outer peripheral side of the separator roll.

<Example 7>
Other than using a resin sheet made of polyethylene having a basis weight of 0.47 mg / cm ² , a thickness of 2.5 μm, a porosity of 48% and an 80 MPa elongation of 153%, and further using magnesia as a filler Produced a separator roll in the same manner as in Example 1.

<Example 8>
Other than using a resin sheet made of polyethylene having a basis weight of 0.5 mg / cm ² , a thickness of 2.5 μm, a porosity of 48% and an 80 MPa elongation of 153%, and further using titania as a filler Produced a separator roll in the same manner as in Example 1.

<Example 9>
Except that a resin sheet made of polyethylene having a basis weight of the filler layer of 0.49 mg / cm ² , a thickness of 2.5 μm, a porosity of 48%, and an 80 MPa elongation rate of 153% was used. A separator roll was prepared.

<Example 10>
A separator roll was produced in the same manner as in Example 9 except that the filler layer side was wound so that the outer surface of the separator roll faced.

<Example 11>
Except that a resin sheet made of polyethylene having a basis weight of the filler layer of 0.47 mg / cm ² , a thickness of 2.5 μm, a porosity of 48%, and an 80 MPa elongation rate of 158% was used, the same as in Example 1. A separator roll was prepared.

<Example 12>
A separator roll was produced in the same manner as in Example 11, except that the filler layer was wound so that the surface on the filler layer side faced the outer peripheral side of the separator roll.

<Example 13>
Except that a resin sheet made of polyethylene having a basis weight of the filler layer of 0.33 mg / cm ² , a thickness of 1.5 μm, a porosity of 38%, and an 80 MPa elongation rate of 128% was used, the same as in Example 1. A separator roll was prepared.

(Performance evaluation)
The separator rolls of Examples 1 to 13 were put into a dryer and left at 80 ° C. for 24 hours. From the separator sheet after the thermal history, a rectangular test piece having a length of 10 cm and a width of 1 cm was sampled, and a mark with a predetermined interval (L0 = 80 mm) was written at the center in the length direction. Both ends of the test piece are fixed to the chuck of a tensile tester (“SV-55C-20M” manufactured by IMADA), and a load is applied to the lower end so as to obtain a tensile stress of 80 MPa. It was measured. The elongation percentage of the separator sheet at this time was calculated by L / L0 × 100. The 80 MPa tensile stress applied in the tensile test corresponds to the standard processing tension applied to the separator sheet in the wound electrode body forming step. Moreover, the surface of the test piece after the said tension test was observed, and the presence or absence of the crack of a filler layer and peeling was confirmed. The results are shown in Table 1. In Table 1, “◯” indicates that there was no crack / peeling, although there was a small crack that can be visually confirmed, but “△” indicates that there is no problem with quality and there is no problem. The case where there was a crack and there was some peeling was indicated as “x”.

  As shown in Table 1, in Example 1 to Example 9 where the elongation percentage of the resin sheet is 160% or less and the elongation percentage of the entire separator sheet including the filler layer is 100% to 111%, cracks and peeling are observed. Not observed at all and good results were obtained. In Examples 10 and 11, there were some small cracks, but there was almost no effect on the quality, and there was no problem. On the other hand, in Examples 12 and 13 in which the elongation percentage of the entire separator sheet including the filler layer exceeded 115%, a large crack was generated and peeling was partially observed. From the viewpoint of suppressing cracks in the filler layer, it is appropriate to set the elongation percentage of the entire separator sheet including the filler layer to about 100% to 115%, preferably about 100% to 111%, particularly preferably. It is about 100% to 110%. Further, from the comparison between Example 9 and Example 10, the direction of winding so that the surface on the filler layer side faces the inner peripheral side of the separator roll is more cracked and peeled than the case of winding so that the outer side faces the outer peripheral side. It was confirmed that it can be more effectively suppressed.

  Test lithium secondary batteries using the separator sheets of Examples 1 to 11 were prepared, and IV resistance was measured. The construction of the test lithium secondary battery was performed as follows.

(Positive electrode sheet)
Lithium nickel cobalt manganese composite oxide (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) powder as a positive electrode active material, acetylene black (AB) as a conductive material, and polyvinylidene fluoride (PVdF) as a binder Were mixed in N-methylpyrrolidone (NMP) so that the mass ratio of these materials was 85: 10: 5 and the solid content was 56 mass%, to prepare a positive electrode active material layer paste. The positive electrode active material layer paste is provided on both sides of the positive electrode current collector by applying the paste for positive electrode active material layer on both sides of a 15 μm thick sheet-like aluminum foil (positive electrode current collector) and drying it. The obtained positive electrode sheet was produced. The coating amount of the positive electrode active material layer paste was adjusted so as to be about 16.8 mg / cm ² (solid content basis) for both surfaces. After drying, pressing was performed so that the density of the positive electrode active material layer was 2.3 g / cm ³ and the thickness of the entire positive electrode sheet was 88 μm.

(Negative electrode sheet)
Carbonaceous powder with amorphous carbon coated on the surface of graphite particles, styrene butadiene rubber (SBR) as a binder and carboxymethyl cellulose (CMC) as a thickener have a mass ratio of 98: 1: 1. The negative electrode active material layer paste was prepared by dispersing in water so that the solid content was 39% by mass. This negative electrode active material layer paste was applied to both sides of a long sheet-like copper foil (negative electrode current collector) having a thickness of 10 μm to produce a negative electrode sheet having a negative electrode active material layer provided on both sides of the negative electrode current collector. . The coating amount of the negative electrode active material layer forming paste was adjusted so that the both surfaces were combined to be about 10.5 mg / cm ² (based on solid content). After drying, the negative electrode active material layer was pressed so that the density of the negative electrode active material layer was 1.4 g / cm ³ and the thickness of the entire negative electrode sheet was 85 μm.

(Lithium secondary battery)
The positive electrode sheet and the negative electrode sheet were overlapped with two separators, wound into a cylindrical shape, and crushed from the side surface direction to obtain a flat wound electrode body. In that case, it arrange | positioned so that the filler layer of a separator sheet might oppose a positive electrode sheet. The wound electrode body thus obtained was housed in a rectangular battery container together with a nonaqueous electrolyte (nonaqueous electrolyte solution), and the opening of the battery container was hermetically sealed. As a non-aqueous electrolyte, about 1.1 mol of LiPF ₆ as a supporting salt in a mixed solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 3: 4: 3. A non-aqueous electrolyte contained at a concentration of 1 liter was used. In this way, a test lithium secondary battery was assembled. The theoretical capacity of this lithium secondary battery is 5.2 Ah.

(Measurement of IV resistance)
IV resistance value was measured about each battery using the separator sheet of Examples 1-11. First, in an environmental atmosphere of 25 ° C., each battery was charged to 4.1 V by 1 C constant current charging, and then discharged to 3 V by 1 C constant current discharging to check the capacity. Then, each battery was charged to 3.537V by 1C constant current charge, and it charged until the electric current value was set to 0.05C by constant voltage charge. Thereafter, discharging was performed at a current value of 20 A for 10 seconds, a voltage value 10 seconds after the start of discharge was measured, and IV resistance was calculated from the voltage change at that time. The results are shown in Table 1.

As shown in Table 1, the smaller the basis weight of the filler layer, the lower the IV resistance and the better the battery characteristics. From the viewpoint of lowering the IV resistance, the basis weight of the filler layer is preferably 0.9 mg / cm ² or less (Examples 1 to 3-11), and more preferably 0.8 mg / cm ² or less (Examples 3 to 11). On the other hand, when the basis weight of the filler layer is too small, the elongation percentage of the separator sheet exceeds 115%, and the filler layer is easily cracked or peeled off (Example 13). From the viewpoint of suppressing cracks and peeling, it is preferable that the basis weight of the filler layer satisfies 0.4 mg / cm ² or more. For example, the basis weight of the filler layer is ^{0.4mg / cm 2 ~0.9mg / cm 2} , preferably those satisfying the 0.5mg ^/ cm ² ~0.8mg ^/ cm 2 is of the filler layer while keeping small IV resistance This is preferable from the viewpoint of suppressing cracking and peeling.

  As mentioned above, although this invention was demonstrated in detail, the said embodiment and a test example are only illustrations, and what was variously modified and changed to the above-mentioned specific example is also contained in the invention disclosed here.

  Note that any of the secondary batteries 100 disclosed herein has performance suitable as a battery mounted on a vehicle. Therefore, according to the present invention, as shown in FIG. 6, a vehicle 1 including any of the secondary batteries 100 disclosed herein is provided. In particular, a vehicle 1 (for example, an automobile) including the secondary battery 100 as a power source (typically, a power source of a hybrid vehicle or an electric vehicle) is provided.

DESCRIPTION OF SYMBOLS 10 Positive electrode sheet 12 Positive electrode collector 14 Positive electrode active material layer 20 Negative electrode sheet 22 Negative electrode collector 24 Negative electrode active material layer 40 Separator sheet 42 Resin sheet 44 Filler layer 50 Container 52 Container body 54 Lid 70 Positive electrode terminal 72 Negative electrode terminal 74 Positive electrode lead terminal 76 Negative electrode lead terminal 80 Winding electrode body 82 Winding core portion 100 Nonaqueous electrolyte secondary battery

Claims (7)

A non-aqueous electrolyte secondary battery comprising a wound electrode body in which a positive electrode sheet and a negative electrode sheet are wound through a separator sheet,
The separator sheet has a porous resin sheet and a porous filler layer laminated on at least one surface of the resin sheet,
The filler layer includes a filler made of an inorganic material and a binder,
The elongation when a tensile stress of 80 MPa is applied in the longitudinal direction of the resin sheet is 160% or less, and
A nonaqueous electrolyte secondary battery having an elongation percentage of 100% to 115% when a tensile stress of 80 MPa is applied in a longitudinal direction of the separator sheet including the filler layer. The weight of the filler layer per unit area of the resin sheet is ^{0.4mg / cm 2 ~0.9mg / cm 2} , a non-aqueous electrolyte secondary battery according to claim 1. The elongation when a tensile stress of 80 MPa is applied in the longitudinal direction of the resin sheet is 150% or less, and
The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein an elongation rate when a tensile stress of 80 MPa is applied in a longitudinal direction of the separator sheet including the filler layer is 100% to 110%.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the resin sheet is made of a polyolefin-based resin.   The non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the filler is made of at least one material selected from the group consisting of alumina, boehmite, magnesia, and titania.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the binder is made of a polymer that is dispersed or dissolved in water. A method for producing a nonaqueous electrolyte secondary battery according to any one of claims 1 to 6, wherein:
Forming a separator sheet by laminating a filler layer containing a filler and a binder made of an inorganic material on one surface of a resin sheet;
Winding the separator sheet containing the filler layer into a roll to form a separator roll; and
A step of constructing a wound electrode body using the separator sheet drawn from the separator roll;
Including
When the separator sheet containing the filler layer is wound into a roll shape to form the separator roll, the separator sheet is wound so that the surface on the filler layer side of the separator sheet faces the inner peripheral side of the separator roll. A method for producing a non-aqueous electrolyte secondary battery.

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